The info on the death cert is telling, the informant(s) don't appear to be family members. Do you recognize who they could be?
Try some back doors. He was married in Russia, so follow the bride. I would obtain the death cert for the Eva (Goetz) Eberle, is this a document you have? Researching her line may reveal where she was from in Russia, and chances are he was from the same or nearby locale. I see there are many Goetz in the Ellis, Kansas in 1880, have you tried to find a connection between them and Eva Goetz? Ask yourself, why did the land in Kansas?
The 1880 Census reveals they were most likely married before 1870 (eldest son born abt 1868 in Russia) and definitely in Russia. They had at least 3 children there before immigrating in 1876.
The 1900 Census indicates he was naturalized. Obtaining the Declaration of Intent (1st papers) might have some data.
Throw a wide net to catch clues.